Conventional PGA sockets comprise a base housing having the corresponding plurality of terminals set in its terminal mounts, which are arranged in the same grid pattern as the lead pins of the pin grid array package, and a slide plate having the corresponding plurality of through holes made and arranged in the same grid pattern. Each through hole corresponds to one of the terminals, and the slide plate is movable between the lead pin-inserting position in which the lead pins of the pin grid array package can be inserted in the through holes and the terminal mounts, requiring little or no pushing force, and the locking position in which the lead pins are applied to, and put in contact with the terminals in the terminal mounts.
The slide plate has slide means to move the slide plate back and forth on the base housing. One example of slide means comprises a cam axle rotatably fixed to one lateral edge and an operating handle attached to one longitudinal side of the base housing for rotating the cam axle, as for instance, is shown in Japanese Patent Application Laid-Open No.7-142134. Another example of slide means comprises a cam member passing through the slide plate and the underlying base housing, and the cam member can be rotated by using a screw driver to move the slide plate on the base housing back and forth, as for instance, is shown in Japanese Patent Application Laid-Open No. 11-513837.
The PGA socket uses the base housing and the slide plate, which can be moved on the base housing back and forth. As a matter of fact, however, these base housing and slide plate are combined together more loosely than required to permit the sliding of the slide plate on the base housing because of the allowance or tolerance. Such significant looseness causes little or no problem, provided that an associated PGA package has so small number of lead pins that adjacent lead pins may be separated a relatively large distance, compared with the allowance. As a general tendency the number of lead pins in PGA sockets has been increasing, and accordingly the pin-to-pin distance has been decreasing to the extent that the excessive looseness may cause an adverse effect in making a required electric connection.